A variety of metallocenes and other single site-like catalysts have been developed to prepare olefin polymers. Metallocenes are organometalic coordination complexes containing one or more xcfx80-bonded moieties (i.e., cyclopentadienyl groups) in association with a metal atom. Catalyst compositions containing metallocenes and other single site-like catalysts are highly useful in the preparation of polyolefins, producing relatively homogeneous copolymers at excellent polymerization rates while allowing one to tailor closely the final properties of the polymer as desired.
Recently, work relating to certain nitrogen-containing, single site-like catalyst precursors has been published. PCT Application No. WO 96/23101 relates to di(imine) metal complexes that are transition metal complexes of bidentate ligands selected from the group consisting of: 
wherein said transition metal is selected from the group consisting of Ti, Zr, Sc, V, Cr, a rare earth metal, Fe, Co, Ni, and Pd;
R2 and R5 are each independently hydrocarbyl or substituted hydrocarbyl, provided that the carbon atom bound to the imino nitrogen atom has at least two carbon atoms bound to it;
R3 and R4 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or R3 and R4 taken together are hydrocarbylene or substituted hydrocarbylene to form a carbocyclic ring;
R44 is hydrocarbyl or substituted hydrocarbyl, and R28 is hydrogen, hydrocarbyl or substituted hydrocarbyl or R44 and R28 taken together form a ring;
R45 is hydrocarbyl or substituted hydrocarbyl, and R29 is hydrogen, substituted hydrocarbyl or hydrocarbyl, or R45 and R29 taken together form a ring;
each R30 is independently hydrogen, substituted hydrocarbyl or hydrocarbyl, or two of R30 taken together form a ring;
each R31 is independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
R46 and R47 are each independently hydrocarbyl or substituted hydrocarbyl, provided that the carbon atom bound to the imino nitrogen atom has at least two carbon atoms bound to it;
R48 and R49 are each independently hydrogen, hydrocarbyl, or substituted hydrocarbyl;
R20 and R23 are independently hydrocarbyl or substituted hydrocarbyl;
R21 and R22 are independently hydrogen, hydrocarbyl or substituted hydrocarbyl; and
n is 2 or 3;
and provided that:
said transition metal also has bonded to it a ligand that may be displaced by or added to the olefin monomer being polymerized; and
when the transition metal is Pd, said bidentate ligand is (V), (VII) or (VIII).
Similarly, PCT Application No. WO 97102298 relates to a process for the polymerization of an olefin, comprising contacting a polymerizable monomer consisting essentially of ethylene, a norbornene or a styrene, with a catalyst system comprising the product of mixing in solution a zerovalent tricoordinate or tetracoordinate nickel compound (II) which has at least one labile ligand, and all ligands are neutral, an acid of the formula HX (IV), and a first compound selected from the group consisting of:
Ar1Qn(III); R8R10Nxe2x80x94CR4R5(CR6R7)mxe2x80x94NR8R10(V); 
wherein:
X is a noncoordinating anion;
Ar1 is an aromatic moiety with n free valencies, or diphenylmethyl;
each Q is xe2x80x94NR2R43 or xe2x80x94CR9xe2x95x90NR3;
R43 is hydrogen or alkyl;
n is 1 or 2;
E is 2-thienyl or 2-furyl;
each R2 is independently hydrogen, benzyl, substituted benzyl, phenyl or substituted phenyl;
each R9 is independently hydrogen or hydrocarbyl; and
each R3 is independently a monovalent aromatic moiety;
m is 1, 2 or 3;
each R4, R5, R6, and R7 is independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
each R8 is independently hydrocarbyl or substituted hydrocarbyl containing 2 or more carbon atoms;
each R10 is independently hydrogen, hydrocarbyl or substituted hydrocarbyl;
Ar2 is an aryl moiety;
R12, R13, and R14 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl or an inert functional group;
R11 and R15 are each independently hydrocarbyl, substituted hydrocarbyl or an inert functional group whose ES is about xe2x88x920.4 or less;
each R16 and R17 is independently hydrogen or acyl containing 1 to 20 carbon atoms;
Ar3 is an aryl moiety;
R18 and R19 are each independently hydrogen or hydrocarbyl;
Ar4 is an aryl moiety;
Ar5 and Ar6 are each independently hydrocarbyl;
Ar7 and Ar8 are each independently an aryl moiety;
Ar9 and Ar10 are each independently an aryl moiety or xe2x80x94CO2R25, wherein R25 is alkyl containing 1 to 20 carbon atoms;
Ar11 is an aryl moiety;
R41 is hydrogen or hydrocarbyl;
R42 is hydrocarbyl or xe2x80x94C(O)xe2x80x94NR41xe2x80x94Ar11;
R44 is aryl;
R22 and R23 are each independently phenyl groups substituted by one or more alkoxy groups, each alkoxy group containing 1 to 20 carbon atoms; and
R24 is alkyl containing 1 to 20 carbon atoms, or an aryl moiety.
PCT Application No. WO 96/33202 relates to a transition metal catalyst containing a pyridine or quinoline moiety and having the formula: 
each R is independently selected from hydrogen or C1 to C6 alkyl, each Rxe2x80x2 is independently selected from C1 to C6 alkyl, C1 to C6 alkoxy, C6 to C16 aryl, halogen, or CF3, M is titanium, zirconium, or hafnium, each X is independently selected from halogen, C1 to C6 alkyl, C1 to C6 alkoxy, or 
L is X, cyclopentadienyl, C1 to C6 alkyl substituted cyclopentadienyl, indenyl, fluorenyl, or 
xe2x80x9cmxe2x80x9d is 0 to 4, and xe2x80x9cnxe2x80x9d is 1 to 4.
Similarly, Fuhrmann et al., Inorg. Chem., 35:6742-6745 (1996) discloses certain Group 4 metal complexes containing amine, amido, and aminopyridinato ligands such as: 
wherein TMS is trimethylsilyl.
An olefin polymerization catalyst composition is described herein having good polymerization activity and productivity. The catalyst composition comprises a heteroatom-containing catalyst precursor having the formula:
AqMLn
wherein each A has the formula: 
M is a metal selected from the group consisting of Group 3 to 13 elements and Lanthanide series elements;
each L is a monovalent, bivalent, or trivalent anion;
X and Y are each heteroatoms;
Cyclo is a cyclic moiety;
each R1 is independently a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group 13 to 17 elements, and two or more adjacent R1 groups may be joined to form a cyclic moiety;
each R2 is independently a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group 13 to 17 elements, and two or more adjacent R2 groups may be joined to form a cyclic moiety;
Q is a bridging group;
each m is independently an integer from 0 to 5;
n is an integer from 1 to 4;
q is 1 or 2;
and when q is 2, the A groups are optionally connected by a bridging group Z.
The catalyst precursor may be conveniently prepared by reacting an organometal compound with a heteroatom-containing ligand of the formula: 
wherein X, Y, Q, Cyclo, R1, R2, and m have the meanings stated above.
The invention provides a catalyst precursor of the formula:
AqMLn
wherein each A has the formula: 
M is a metal selected from the group consisting of Group 3 to 13 elements and Lanthanide series elements;
each L is a monovalent, bivalent, or trivalent anion;
X and Y are each heteroatoms;
Cyclo is a cyclic moiety;
each R1 is independently a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group 13 to 17 elements, and two or more adjacent R1 groups may be joined to form a cyclic moiety;
each R2 is independently a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group 13 to 17 elements, and two or more adjacent R2 groups may be joined to form a cyclic moiety;
Q is a bridging group;
each m is independently an integer from 0 to 5;
n is an integer from 1 to 4;
q is 1 or 2;
and when q is 2, the A groups are optionally connected by a bridging group Z; along with a catalyst composition comprising this catalyst precursor and an activating cocatalyst, as well as a process for the polymerization of olefins, using this catalyst composition.
The invention also provides a catalyst precursor comprising the reaction product of an organometal compound and heteroatom-containing ligand having a formula selected from the group consisting of: 
wherein X and Y are each heteroatoms;
Cyclo is a cyclic moiety;
each R1 is a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group 13 to 17 elements, and two or more adjacent R1 groups may be joined to form a cyclic moiety;
each R2 is a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group 13 to 17 elements, and two or more adjacent R2 groups may be joined to form a cyclic moiety;
Q is a bridging group; and
each m is independently an integer from 0 to 5; as well as a catalyst composition comprising this catalyst precursor and an activating cocatalyst, and a process for polymerizing olefins using this catalyst composition.
The catalyst precursor may have the formula:
AqMLn
In the above formula, each A has the formula: 
M is a metal selected from the group consisting of Group 3 to 13 and Lanthanide series elements, preferably a Group 4 element, more preferably zirconium.
Each L is a monovalent, bivalent, or trivalent anion, preferably independently selected from the group consisting of halogens; hydrogen; alkyl, aryl, alkenyl, alkylaryl, arylalkyl, hydrocarboxy radicals having 1-50 carbon atoms; amides; phosphides; sulfides; silylalkyls; diketonates; and carboxylates. More preferably, each L is selected from the group consisting of halides, alkyl radicals, and arylalkyl radicals. Most preferably, each L is selected from the group consisting of arylalkyl radicals such as benzyl. Each L may contain one or more heteroatoms.
X and Y are each heteroatoms and are preferably independently selected from the group consisting of N, O, S, and P. More preferably, X and Y are independently selected from the group consisting of N and P. Most preferably, X and Y are both nitrogen.
Y is contained in a heterocyclic ring containing 2 to 7 carbon atoms, preferably 3 to 6 carbon atoms, more preferably 5 carbon atoms. The heterocyclic ring may contain additional heteroatoms (i.e., in addition to Y).
Cyclo is a cylic moiety. Preferably, Cyclo is a carbocyclic ring containing 3 to 7 carbon atoms. More preferably, Cyclo is an aryl group.
Each R1 is independently a group containing 1 to 50 carbon atoms selected from the group consisting of hydrogen and Group 13 to 17 elements, and two or more adjacent R1 groups may be joined to form a cyclic moiety such as an aliphatic or aromatic ring. Preferably, R1 is an alkyl. More preferably, R1 is isopropyl. Optionally, an R1 group may be joined to Q. It is preferred that at least one R1 is ortho to X.
Each R2 is independently a group containing 1 to 50 atoms selected from the group consisting of hydrogen and Group 13 to 17 elements, and two or more adjacent R2 groups may be joined to form a cyclic moiety such as an aliphatic or aromatic ring. Preferably, R2 is hydrogen or an aryl. More preferably, R2 is hydrogen. When R2 is an aryl group and Y is N a quinoline group may be formed. Optionally, an R2 group may be joined to Q.
Q is a bridging group. Preferably, Q contains one or more Group 13, 14, 15, or 16 elements. More preferably, Q contains one or more Group 14 elements. Most preferably, Q is a substituted carbon.
Each m is independently an integer from 0 to 5, preferably 2, and n is an integer from 1 to 4, preferably 3.
The letter q is 1 or 2, and when q is 2 the A groups are optionally connected by a bridging group Z. When present, Z preferably contains one or more Group IIIA, Group IVA, Group VA, or Group VIA elements. More preferably, Z contains one or more Group IVA elements.
In one embodiment of the invention, the catalyst precursor has the formula: 
wherein Ra and Rb are each independently selected from the group consisting of alkyl, aryl, heterocyclic groups, and hydrogen; Rc and Rd are each independently selected from the group consisting of alkyl, aryl, and hydrogen; and each L has the meaning stated above.
In another embodiment of the invention, the catalyst precursor has the formula: 
wherein Ra, Rb, Rc, Rd, and L have the meanings stated above.
In yet another embodiment of the invention, the catalyst precursor has the formula: 
wherein Ra, Rb, Rc, Rd, and L have the meanings stated above.
In a further embodiment of the invention, the catalyst precursor has the formula: 
wherein Ra, Rb, Rc, Rd, and L have the meanings stated above.
In a particularly preferred embodiment of the invention, the catalyst precursor has the formula: 
In another particularly preferred embodiment of the invention, the catalyst precursor has the formula: 
In further particularly preferred embodiment of the invention, the catalyst precursor has the formula: 
Yet another preferred catalyst precursor is: 
The catalyst precursor may be made by any method. The method of making the catalyst precursor is not critical to the invention. However, one useful method of making the catalyst precursor is by reacting an organometal compound or a metal halide with a heteroatom-containing ligand having a formula selected from the group consisting of: 
wherein X, Y, Q, Cyclo, R1, R2, and m have the meanings stated above.
Preferably, the catalyst precursor is made by reacting an organometal compound with the heteroatom-containing ligand. Accordingly, in one embodiment of the invention, the catalyst precursor comprises the reaction product of an organometal compound and a heteroatom-containing ligand having a formula selected from the group consisting of: 
wherein X, Y, Q, Cyclo, R1, R2, and m have the meanings stated above.
The metal of the organometal compound may be selected from Group 3 to 13 elements and Lanthanide series elements. Preferably, the metal is a Group 4 element. More preferably the metal is zirconium.
The organometal compound for example may be a metal hydrocarbyl such as a metal alkyl, metal aryl, or metal arylalkyl. Metal silylalkyls, metal amides, or metal phosphides may also be used. Preferably, the organometal compound is a zirconium hydrocarbyl. More preferably, the organometal compound is a zirconium arylalkyl. Most preferably, the organometal compound is tetrabenzylzirconium.
Examples of useful organometal compounds are tetramethylzirconium, tetraethylzirconium, tetrakis[trimethylsilylmethyl]zirconium, tetrakis[dimethylamino]zirconium, dichlorodibenzylzirconium, chlorotribenzylzirconium, trichlorobenzylzirconium, bis[dimethylamino]bis[benzyl]zirconium, and tetrabenzylzirconium.
Tetramethyltitanium, tetraethyltitanium, tetrakis[trimethylsilylmethyl]titanium, tetrakis[dimethylamino]titanium, dichlorodibenzyltitanium, chlorotribenzyltitanium, trichlorobenzyltitanium, bis[dimethylamino]bis[benzyl]titanium, and tetrabenzyltitanium.
Tetramethylhafnium, tetraethylhafnium, tetrakis[trimethylsilylmethyl]hafnium, tetrakis[dimethylamino]hafnium, dichlorodibenzylhafnium, chlorotribenzylhafnium, trichlorobenzylhafnium, bis[dimethylamino]bis[benzyl]hafnium, and tetrabenzylhafnium.
Tetrakis[tertbutyl]lanthanates; lithiumhexamethyllanthanates; tetrakis[allyl]lanthanates; and tris[bis[trimethylsilyl]methyl]lanthanides.
Because organometal compounds containing lanthanides and some transition metals are often difficult to prepare, it is preferred to prepare catalyst precursors containing these in a two-step process by first reacting the heteroatom-containing ligand with a lithium alkyl to make a lithium amide, and then reacting with a lanthanide or transition metal halide to generate the amide complex.
The heteroatom-containing ligand has the formula: 
wherein X, Y, Q, Cyclo, R1, R2, and m have the meanings stated above.
Preferably, the heteroatom-containing ligand has the formula: 
More preferably, the heteroatom-containing ligand is a pyridine/imine ligand of the formula: 
wherein each Rxe2x80x2 is a hydrocarbon group containing 1 to 20 carbon atoms and two or more adjacent Rxe2x80x2 groups may be joined to form an aliphatic or aromatic ring;
each Rxe2x80x3 is a hydrocarbon group containing 1 to 20 carbon atoms and two or more adjacent Rxe2x80x3 groups may be joined to form an aliphatic or aromatic ring; and
R3 is hydrogen, a hydrocarbon group containing 1 to 20 carbon atoms optionally substituted with one or more heteroatoms, or a heteroatom optionally substituted with a hydrocarbon group.
For example, Compound 1 may be made by reacting a substituted pyridine/imine ligand with a zirconium aryl such as tetrabenzyl zirconium: 
This reaction is preferably carried out in a suitable solvent such as toluene or benzene at a temperature in the range of xe2x88x9250 to 50xc2x0 C. and a pressure ranging from a vacuum to 1000 psi.
Alternatively and preferably, the catalyst precursor can be made by reacting the heteroatom-containing ligand with a metal halide and then further reacting the product thereof with a Grignard reagent, such as an organomagnesium halide. For instance, the same catalyst precursor, Compound 1, may be made by reacting a substituted pyridine/imine ligand with a zirconium halide such as zirconium tetrachloride, and then further reacting the product thereof with PhCH2MgCl.
Another preferred catalyst precursor, Compound 2, may be made by reacting a substituted pyridine/amine ligand with a zirconium aryl such as tetrabenzyl zirconium: 
This reaction is preferably carried out in a suitable solvent such as toluene or benzene at a temperature in the range of xe2x88x9250 to 50xc2x0 C. and a pressure ranging from a vacuum to 1000 psi.
Another preferred catalyst precursor, Compound 3, may be made by reacting Compound 2 with acetone: 
As another example, Compound 4 may be made in a multistep procedure by reacting a substituted pyridine/amine ligand sequentially with methyl lithium, chlorotrimethylsilane, zirconium tetrachloride, and benzyl magnesium chloride as follows: 
This reaction is preferably carried out in a suitable solvent such as toluene or benzene at a temperature in the range of xe2x88x9250 to 50xc2x0 C. and a pressure ranging from a vacuum to 1000 psi.
The catalyst precursor may be isolated by conventional methods.
The catalyst composition comprises the catalyst precursor and an activating cocatalyst. The activating cocatalyst is capable of activating the catalyst precursor. Preferably, the activating cocatalyst is one of the following: (a) branched or cyclic oligomeric poly(hydrocarbylaluminum oxide)s which contain repeating units of the general formula xe2x80x94(Al(R*)O)xe2x80x94, where R* is hydrogen, an alkyl radical containing from 1 to about 12 carbon atoms, or an aryl radical such as a substituted or unsubstituted phenyl or naphthyl group; (b) ionic salts of the general formula [A+][BR**4xe2x88x92], where A+ is a cationic Lewis or Bronsted acid capable of abstracting an alkyl, halogen, or hydrogen from the metallocene catalysts, B is boron, and R** is a substituted aromatic hydrocarbon, preferably a perfluorophenyl radical; (c) boron alkyls of the general formula BR**3, where R** is as defined above; or mixtures thereof. The activating cocatalyst may also be an organoaluminum compound, such as triisobutylaluminum or diethylaluminum chloride.
Preferably, the activating cocatalyst is a branched or cyclic oligomeric poly(hydrocarbylaluminum oxide) or a boron alkyl. More preferably, the activating cocatalyst is an aluminoxane such as methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), or a boron alkyl.
Aluminoxanes are well known in the art and comprise oligomeric linear alkyl aluminoxanes represented by the formula: 
and oligomeric cyclic alkyl aluminoxanes of the formula: 
wherein s is 1-40, preferably 10-20; p is 3-40, preferably 3-20; and R*** is an alkyl group containing 1 to 12 carbon atoms, preferably methyl.
Aluminoxanes may be prepared in a variety of ways. Generally, a mixture of linear and cyclic aluminoxanes is obtained in the preparation of aluminoxanes from, for example, trimethylaluminum and water. For example, an aluminum alkyl may be treated with water in the form of a moist solvent. Alternatively, an aluminum alkyl, such as trimethylaluminum, may be contacted with a hydrated salt, such as hydrated ferrous sulfate. The latter method comprises treating a dilute solution of trimethylaluminum in, for example, toluene with a suspension of ferrous sulfate heptahydrate. It is also possible to form methylaluminoxanes by the reaction of a tetraalkyl-dialuminoxane containing C2 or higher alkyl groups with an amount of trimethylaluminum that is less than a stoichiometric excess. The synthesis of methylaluminoxanes may also be achieved by the reaction of a trialkyl aluminum compound or a tetraalkyldialuminoxane containing C2 or higher alkyl groups with water to form a polyalkyl aluminoxane, which is then reacted with trimethylaluminum. Further modified methylaluminoxanes, which contain both methyl groups and higher alkyl groups, i.e., isobutyl groups, may be synthesized by the reaction of a polyalkyl aluminoxane containing C2 or higher alkyl groups with trimethylaluminum and then with water as disclosed in, for example, U.S. Pat. No. 5,041,584.
When the activating cocatalyst is a branched or cyclic oligomeric poly(hydrocarbylaluminum oxide), the mole ratio of aluminum atoms contained in the poly(hydrocarbylaluminum oxide) to total metal atoms contained in the catalyst precursor is generally in the range of from about 2:1 to about 100,000:1, preferably in the range of from about 10:1 to about 10,000:1, and most preferably in the range of from about 50:1 to about 2,000:1. When the activating cocatalyst is an ionic salt of the formula [A+][RR**4xe2x88x92] or a boron alkyl of the formula BR**3, the mole ratio of boron atoms contained in the ionic salt or the boron alkyl to total metal atoms contained in the catalyst precursor is generally in the range of from about 0.5:1 to about 10:1, preferably in the range of from about 1:1 to about 5:1.
The catalyst precursor, the activating cocatalyst, or the entire catalyst composition may be impregnated onto a solid, inert support, in liquid form such as a solution, dispersion or neat liquid, spray dried, in the form of a prepolymer, or formed in-situ during polymerization. Particularly preferred among these is a catalyst composition that is spray dried as described in European Patent Application No 0 668 295 A1 or in liquid form as described in U.S. Pat. No. 5,317,036.
In the case of a supported catalyst composition, the catalyst composition may be impregnated in or deposited on the surface of an inert substrate such as silica, carbon black, polyethylene, polycarbonate porous crosslinked polystyrene, porous crosslinked polypropylene, alumina, thoria, zirconia, or magnesium halide (e.g., magnesium dichloride), such that the catalyst composition is between 0.1 and 90 percent by weight of the total weight of the catalyst composition and the support.
The catalyst composition may be used for the polymerization of olefins by any suspension, solution, slurry, or gas phase process, using known equipment and reaction conditions, and is not limited to any specific type of reaction system. Generally, olefin polymerization temperatures range from about 0xc2x0 C. to about 200xc2x0 C. at atmospheric, subatmospheric, or superatmospheric pressures. Slurry or solution polymerization processes may utilize subatmospheric or superatmospheric pressures and temperatures in the range of about 40xc2x0 C. to about 110xc2x0 C. A useful liquid phase polymerization reaction system is described in U.S. Pat. 3,324,095. Liquid phase reaction systems generally comprise a reactor vessel to which olefin monomer and catalyst composition are added, and which contains a liquid reaction medium for dissolving or suspending the polyolefin. The liquid reaction medium may consist of the bulk liquid monomer or an inert liquid hydrocarbon that is nonreactive under the polymerization conditions employed. Although such an inert liquid hydrocarbon need not function as a solvent for the catalyst composition or the polymer obtained by the process, it usually serves as solvent for the monomers employed in the polymerization. Among the inert liquid hydrocarbons suitable for this purpose are isopentane, hexane, cyclohexane, heptane, benzene, toluene, and the like. Reactive contact between the olefin monomer and the catalyst composition should be maintained by constant stirring or agitation. The reaction medium containing the olefin polymer product and unreacted olefin monomer is withdrawn from the reactor continuously. The olefin polymer product is separated, and the unreacted olefin monomer and liquid reaction medium are recycled into the reactor.
Preferably, gas phase polymerization is employed, with superatmospheric pressures in the range of 1 to 1000 psi, preferably 50 to 400 psi, most preferably 100 to 300 psi, and temperatures in the range of 30 to 130xc2x0 C., preferably 65 to 110xc2x0 C. Stirred or fluidized bed gas phase reaction systems are particularly useful. Generally, a conventional gas phase, fluidized bed process is conducted by passing a stream containing one or more olefin monomers continuously through a fluidized bed reactor under reaction conditions and in the presence of catalyst composition at a velocity sufficient to maintain a bed of solid particles in a suspended condition. A stream containing unreacted monomer is withdrawn from the reactor continuously, compressed, cooled, optionally fully or partially condensed as disclosed in U.S. Pat. Nos. 4,528,790 and 5,462,999, and recycled to the reactor. Product is withdrawn from the reactor and make-up monomer is added to the recycle stream. As desired for temperature control of the system, any gas inert to the catalyst composition and reactants may also be present in the gas stream. In addition, a fluidization aid such as carbon black, silica, clay, or talc may be used, as disclosed in U.S. Pat. No. 4,994,534.
Polymerization may be carried out in a single reactor or in two or more reactors in series, and is conducted substantially in the absence of catalyst poisons. Organometallic compounds may be employed as scavenging agents for poisons to increase the catalyst activity. Examples of scavenging agents are metal alkyls, preferably aluminum alkyls, most preferably triisobutylaluminum.
Conventional adjuvants may be included in the process, provided they do not interfere with the operation of the catalyst composition in forming the desired polyolefin. Hydrogen or a metal or non-metal hydride, e.g., a silyl hydride, may be used as a chain transfer agent in the process. Hydrogen may be used in amounts up to about 10 moles of hydrogen per mole of total monomer feed.
Olefin polymers that may be produced according to the invention include, but are not limited to, ethylene homopolymers, homopolymers of linear or branched higher alpha-olefins containing 3 to about 20 carbon atoms, and interpolymers of ethylene and such higher alpha-olefins, with densities ranging from about 0.86 to about 0.96. Suitable higher alpha-olefins include, for example, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 3,5,5-trimethyl-1-hexene. Olefin polymers according to the invention may also be based on or contain conjugated or non-conjugated dienes, such as linear, branched, or cyclic hydrocarbon dienes having from about 4 to about 20, preferably 4 to 12, carbon atoms. Preferred dienes include 1,4-pentadiene, 1,5-hexadiene, 5-vinyl-2-norbornene, 1,7-octadiene, vinyl cyclohexene, dicyclopentadiene, butadiene, isobutylene, isoprene, ethylidene norbornene and the like. Aromatic compounds having vinyl unsaturation such as styrene and substituted styrenes, and polar vinyl monomers such as acrylonitrile, maleic acid esters, vinyl acetate, acrylate esters, methacrylate esters, vinyl trialkyl silanes and the like may be polymerized according to the invention as well. Specific olefin polymers that may be made according to the invention include, for example, polyethylene, polypropylene, ethylene/propylene rubbers (EPR""s), ethylene/propylene/diene terpolymers (EPDM""s), polybutadiene, polyisoprene and the like.
The following examples further illustrate the invention.